Stress migration is a failure mechanism that often occurs in
integrated circuit metallization (
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
,
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
). Voids form as result of vacancy migration driven by the
hydrostatic
Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...
stress gradient. Large voids may lead to open circuit or unacceptable resistance increase that impedes the IC performance. 'Stress migration is often referred as stress voiding, stress induced voiding or SIV.
High temperature processing of copper dual damascene structures leaves the copper with a large tensile stress due to a mismatch in coefficient of thermal expansion of the materials involved. The stress can relax with time through the diffusion of vacancies leading to the formation of voids and ultimately open circuit failures.
[Stress Migration and the Mechanical Properties of Copper, G.B. Alers, et al]
References
Semiconductor device fabrication
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